1. Field of the Invention
The present invention is directed to a hot water supplying system for supplying hot water to bathroom faucets such as for bathtubs, basins, and showers.
2. Description of the Prior art
There have been provided in the art a hot water supply system which mixes water flowing from hot and cold water sources to discharge through an outlet the mixed water at a desired temperature. The system utilizes a mixing valve movable within a mixing chamber in fluid communication respectively with the hot and cold water sources. The mixing valve is operably connected to a handle or controller to be driven thereby to move into a suitable position within the mixing chamber in order to mix the hot and cold water at a suitable proportion for supplying the water at a temperature selected at the handle or the controller. The mixing valve is preferably of temperature-responsive type to effect self-adjusting the temperature of the water being discharged in an open loop control manner. Such open loop control is essential and advantageous rather than a feed back control for the purpose of operating the system in a fail-safe manner at the start of discharging the hot water in that it can certainly prevent the discharge of the water having a temperature higher than intended that may cause scalding. In other words, if the feed back control is utilized to control the water temperature at the start of discharging the hot water while monitoring the temperature of the water being discharged, there is no hot water being discharged so that the system would monitor the temperature of the remaining water in the mixing chamber which temperature is sometimes considerably low as it may has been cooled after the previous hot water supplying. Consequently, the system would respond in a feed back manner to rush the hot water of high temperature in excess proportion in an attempt to compensate for such low temperature. However, the result is that an excess amount of the hot water at a temperature higher than intended would be discharged, which is not expected by the user and is very dangerous to the user. Therefore, the feed back control should be avoided at the start of discharging the hot water for avoiding scalding or other hazard resulting from unexpectedly high temperature water, although it is effective for temperature control while the hot water is constantly discharged.
In view of the above, the open loop control is preferred at each start of discharging the hot water to make the system fail-safe. In fact, the open loop control has been accepted also because of its simple structure and of less cost requirement. As described in the above, the prior hot water supply system of open loop temperature control type generally utilizes the mixing valve of self-adjusting capability in response to the temperature of the water being discharged. Such mixing valve incorporates, for example, so called a thermo wax having high thermal dilative properties by which the valve position is self-adjusted independently of the handle and the controller. Although the open loop temperature control using the mixing valve of self-adjusting type is generally acceptable, it may cause a problem that the temperature of the hot water being discharged is deviated or shifted critically from the temperature selected by the user depending upon a particular installation site. The inconsistency between the actual temperature of the water and the temperature intended by the user comes from the fact that the temperature and pressure of the hot water as well as the cold water fed to the system from the individual sources may vary with different installation sites. To compensate for such varying conditions associated with the particular installation site, the prior art system is required at its initial installation to adjust the position of the mixing valve mechanically by the use of a special jig or tools. However, such adjustment is generally made by a skilled person well understanding the mechanical structure of the system and is inconvenient particularly for a person not knowing the structure of the system.